Jeerasak Pitakarnnop, Rugkanawan Wongpithayadisai, Suwat Phanakulwijit
ALTERNATIVE MODELS AND NUMERICAL SIMULATIONS OF RAREFIED GAS FLOW IN VACUUM SYSTEMS

An analytical and a numerical studies of rarefied gas effects on the flow through a vacuum pipe at low operating pressure are performed by the use of both continuum and kinetic approaches. The pipe operates in a high-Knudsen-, low-Reynolds numbers regime where the viscous effects dominate the flow. Since only the isothermal flow is focused, the slip-flow at the wall is the main anomaly. A comparison of the calculation results with those from the available measurements shows good agreement.

Hiroaki Kajikawa, Tokihiko Kobata
APPLICATION OF 0-A-0 PRESSURIZATION TO PRESSURE GAUGE CALIBRATIONS

A new calibration method is proposed and examined to improve the pressure calibration using pressure gauges as the reference device. In the method, the reference gauge is pressurized with the 0-A-0 procedure, while the test gauge can be pressurized with various procedures. The calibration results with this method were found to be consistent with those calibrated against a pressure balance. The method is expected to help develop more precise and low-cost pressure calibration systems.

Jay H. Hendricks, Jacob E. Ricker, Jack A. Stone, Patrick F. Egan, Gregory E. Scace, Gregory F. Strouse, Douglas A. Olson, Donavon Gerty
MEASURING PRESSURE AND VACUUM WITH LIGHT: A NEW PHOTONIC, QUANTUM-BASED, PRESSURE STANDARD

The future of pressure and vacuum measurement will rely on lasers and Fabry–Pérot optical cavities, and will be based on fundamental physics of light interacting with a gas. Light interacts with matter such that light travels at a slower speed and has shorter wavelength in gas than it does in vacuum. A photonic-based pressure standard represents a disruptive change in the way of realizing and disseminating the SI unit of pressure, the pascal. The underlying metrology behind the advance is the ultra-accurate determination of the refractive index of a gas by picometer optical interferometry, and when value for molar refractive index is calculated from ab-initio quantum chemistry calculations it provides a quantum-based primary pressure standard. The aim of the project is a new technique that will improve accuracy and enable the complete replacement of all mercury-based pressure standards. The National Institute of Standards and Technology (NIST) has now built a working prototype of a fixed length optical cavity (FLOC) with impressive preliminary results. NIST is also developing an even more accurate variable length optical cavity (VLOC) that will make simultaneous ultra-precise measurements of vacuum and gas cavity optical lengths. This paper covers the current status and early prototype results of the photonic-based pressure standard. The early results from the FLOC have exceeded first experimental expectations in that the photonic-based standard is fast, sensitive, accurate, and wide range. Early results demonstrate a pressure resolution of 0.1 mPa (7.5 × 10^-7 Torr), outperforming the NIST ultrasonic interferometer manometer by 35X. The lowest pressure measured is 10X more sensitive (1 mPa vs. 10 mPa). Accuracy of the photonic based pressure standard varies between 0.02 parts in 100 (%) at medium vacuum (1 kPa) to 35 mPa/kPa (35 parts in 10⁶) at atmospheric pressure (~100 kPa), with repeatability of 5 mPa/kPa (5 parts in 10⁶) or better, indicating that the standard, once fully developed, will effectively replace mercury manometers for the barometric pressure range, providing improved functionality without the associated hazards of mercury.

Yasin Durgut, Gökçe Sevim Sarıyerli
THE CHARACTERIZATION OF FPG (FORCE-BALANCED PISTON GAUGE) IN ABSOLUTE MODE IN TUBITAK UME PRESSURE LABORATORY

TUBITAK UME has been using FPG system which was developed by DH Instruments Inc. since 2013. FPG system covers the range of gauge and absolute pressure from less than 1 Pa to 15 kPa. The system uses a mass comparator to measure the force resulting from differential pressure across a non-rotating piston in a close fitting cylinder. Resolution is up to 1 mPa and measurement uncertainty as low as ± (5 mPa + 3 · 10^-5 · p) is estimated. The most important advantage of FPG is the fact that a conventional pressure balance can be used to determine the effective area. However, the measurement is not straight forward due to the lubrication gas flow in the FPG. The validation and metrological characterization of the new instrument is a challenge for UME and it’s more convenient to join international comparison to provide the traceability of measurement results.
This paper describes the metrological characterization of FPG in gauge and in absolute modes.

Jaromír Volf , Viktor Novák, Volodymyr Ryzhenko
USING OF CONDUCTIVE INK IN THE PLANTOGRAF MEASURING SYSTEM

The present paper deals with tactile sensors with circular electrodes in which conductive ink was used as a converter converting pressure into an electric signal. On a robotized measuring post, the dependence of the resistance on the thickness of the deposited ink layer was studied and the results were compared. The sensitivity of the individual setups is evaluated and presented graphically. Also the properties of identical tactile sensors in which a conductive elastomer Yokohama rubber CS57-7RSC was used were compared with those with conductive ink.